Currently, a gate electrode or source-drain electrode in the LCD or OLED display field uses conventionally pure aluminum or aluminum alloy to make an intermediate layer to form a three-layer electrode, for example, Mo/Al/Mo pure aluminum electrode or Mo/AlFe/Mo, Mo/AlCo/Mo, Mo/AlNi/Mo aluminum alloy electrode. The bottom layer and the top layer of such pure aluminum electrode or aluminum alloy electrode are Mo metallic layers, while for a pure aluminum electrode, an Al metallic layer is located between the bottom layer and the top layer, and for an aluminum alloy electrode, an aluminum alloy such as AlFe, AlCo or AlNi is located between the bottom layer and the top layer. Conventionally in the art, an Mo layer first formed by depositing or sputtering, etc. on a glass substrate or an ITO film layer is referred to as the bottom layer, and then an Al layer or aluminum alloy layer is formed as the intermediate layer, and an Mo layer is again formed subsequently as the top layer.
However, in the prior art, the power lines as etched will have irregular breaches at the edge which resemble traces from biting of a mouse, and this phenomenon is termed “mouse bite” in the art, as shown in the elliptic shape in FIG. 1. Further, during etching of the power lines, the etching liquid would in theory attack downward or upward vertically, but as the action of the etching liquid is not directional indeed, it produces side etching such that the conductor lines after the etching exhibit inversions at both sides in cross-section, and this phenomenon is termed “undercut” in the art, as shown in the elliptic shape in FIG. 2.
The above-mentioned mouse bite and undercut phenomena cause easily a short circuit of the power lines or a signal delay, and such problems in turn slow down the progress of electrode thinning and influence the advancement of high-resolution products. In addition, when the undercut exists in the electrode, a disconnection of the electrode may arise easily, leading to lowered performances of the electronic product, such as dark spots in an LCD or OLED display.
Past experience for solving the mouse bite problem in pure aluminum or aluminum alloy electrodes is changing the etching liquid. However, in case of the production line for mass production of variety products, this method requires changing a former conventional etching liquid during which the production of other products will be influenced, and also the re-verification and test of the etching liquid requires longer time.
Furthermore, if the profile angle in the electrode is undesirable, it would result in a relatively large segment difference (a difference between the high and low planes of the thin film) upon lap-joints of the upper film layer and thus in disconnection problem which would influence the yield of the product. For example, such a situation is shown in the elliptic shape in FIG. 3. In FIG. 3, the profile angle is approximately between 70° C. and 80° C. resulting in a relatively large segment difference, which is volunerable to disconnection problem and influences the yield of the product.
Therefore, there is an urgent need for solving the existing mouse bite, undercut, undesirable profile angle, etc. in the prior art.